Industrial applications continue to require semiconductor devices with more demanding specifications. To meet the increasing demand, most modern semiconductor fabrication processes include thin film metrology systems and other optical systems to obtain characteristic information about thin films formed on a given semiconductor wafer, such as a silicon wafer. For example, thin films may include oxide, nitride, and/or metal layers, among others. Characteristics such as the thickness and composition of each thin film must be tightly controlled during the manufacturing process to ensure proper performance of the resulting semiconductors. Accordingly, optical systems are used at various steps throughout the semiconductor manufacturing process.
The accuracy of most modern optical systems is limited, however, by atmospheric molecular contamination “AMC” that may accumulate on the surface of a thin film and distort the film thickness or other physical characteristic measured or analyzed by an ellipsometer or other optical system. Atmospheric molecular contaminants can be removed from the surface of a thin film with a variety of techniques such as the use of energy beams or heating to a sufficiently high temperature. However, AMC continues to accumulate in the interim period between AMC removal and taking characteristic measurements. Therefore, it is necessary to inhibit re-accumulation of AMC on a thin film surface after it is cleaned in order to make accurate characteristic measurements and observations. Accordingly, the present invention overcomes the foregoing problems by providing an efficacious and relatively inexpensive solution for controlling AMC accumulation.